Semi-automatic telephone-exchange trunking system.



i. Mmmm l SEMI-Auommc IELEPHUNE. EXCHANGE 'murmm'svsm APPLIGT'IWHLED,Jee. 5.1910- Patented Apr. 6,1915.

` 4 sHnBTsHsHEE'r 1.

gr@ i A Mlmmur E. A. MELL|NGER. 'SEMI-AUTOMATIC TELEPHONE EXCHANGE TRUNKING SYSTEM.

APPLICATION FILED FEB. 5| 1910. Y A 1,134,978. y Patented-@M1915 '4' links-SHEET 2.

ada@ @ml M APPLlcAloN- man rse. s. 1916.

Pgnteu Apr, e, 1915 ...Am wm* www Amb,

:Be fit iii-noi:

nenne o" @ne Yinited Stai resident of Chicffigox `iooil; yi invened e Cei i npnevenien in 'Sen i-ii.

einen ichites to eiephone Systems which boh manuel and employed-for extend- 'fr'oin n Ceiling -ine iidy o. in ihe nature of on @spending ippiie 369,012, ,e -i i and eine of this character it Y'o`-`counse, .that 'the manual y S tei'ibo'91rdl finement 'through Whose board 20'V4 the ceiiles es' sini-Mheve 'supervision of the @e we@ ing i Subscriber i .operator eine for recei' ei signal subscriber hangen@ his W y the snfitchboird ops h-e serninuemetieaiiy es- 'ff connection between vthe is obvious, however, vefrengemenit v1which will i i i l 'Of Combined' :iut-o'- runking servi ee' ii'iii not hefobjeets of my invent-ion 'isi -hefpifovision of e' supervisory fi'or nee in conjunction with a nario 'service in which only bvo ore employed -beween the seie V. eonneeiore which 'is often for, example., in systems Whieh 1 n he district pien, each une ivjiiiiihe centi-Tai 'station bjr- Ineens meiner.iuililiery trunks, and each suhntrgiistu tionhm'ing there-ut oni;r the lines. i "eribers who are Within 'that i n uiiir i ALetrief. in such ense` of course,

n 1 1 the supervision oi the eonnecion, im?

yii-lied,subserber is concerned, must be h eiuo-iiiire i;rilnke iieteeen-he inain .sntions, and hen for 'the iidisiinee over sifitehboerd. Thus,

Speciiaaeon of Letters Fatent.

MjnL- es of i enge: Trunking Systems, of

*ion e'fziinpie, by receiving a 1ere the sitnu'iion is more g iilsubceniri stati on which: is

#ny suitable' gifenreoieiiajfn enrinnonninnnenen Tnnnmne SYSTEM;

nieuwe epi; 6,1915.

'.ppleaion'led February 5, 19H2. i Serial No. :S-2,394.

1n a system characterized by my .inventionthe caiied subscriber. when he henfs'no his receiver, bruns 'ts ehe super signin over tiro sides of i porti oi' ine ing circuit in series, and for in@l remainder of the diszinee over hird conductors tha are exeiuded from 'the talking circuit und which form :i eircuiiy extending to the nien un] swiehboarch in this W115i the niannui sifiichbourd opeizior receives u signal when he cnied subscriber hangs up his receiver which indiee'es. ffnet the subscribers sire h rougir iiikin Another object to provide sngeri'isory connector switch, and meansfor switching e high resistance into eirouit witi. `he trunk line ieading to such connector when the called subscriber answers, thus retiring the supervisory signal and thereby. indicating io the operator that the Cali vhas been unsn'ered; and whereby, when the oaiied subscriber hangs up his receiver, the resistance of the supervisory Circuit over the trunk line Will bereduced byehort-eireuiting said resistance, thereby causing the. supervisory eign-ai to be again displayed, indient-ing that ehe subscribers are through talking'.

Another object is to provide repeater of such character thatit lWiii not only repea the ceiling impulses, but ijvii also serve as "he inediuin for transferring the supervisorjiv gneis "from the talking circuit tothe trunkre'lezise circuit when the called subscriber Answers, or when the called subscriber hangs up his receiver, whereby the supervision is, as previously stated, partly over the talking circuit, and then for the balance of the distance over the third conductors of the trunk lines to the manual switchboard.

E is also an .object to provide Cert-ain deteils und features 'of improvement and coinbinations vtending to inereasethe general efficiency of a Semi-automatic or combined manual and automatic' telephone exchange system.

station A" (Fig. said connection eine ploying apparatus embodying the principles of my inveniion.

"in Fig. l is shown a nien iai-substation Wlh en euon'ia-ic individual or line switch C. for extending connection from the station line conducto-rs to trunk'conductors 7 for'connecting jacks j and j.' The jack j .is connected to a trunk line leading from the sub-exchange of Fig. 1. The jack j is' substation A. there is allotted at the eX- connected to a trunk line leading to-an automatic selector switch E (Fig. 3). A t vS'is shown an operators talking setr In Fig. 3 there is shown automatic switching apparatus consisting of a so-called first selector E, second selector F and my' im provedrepeater H.

In Fig. 4 there isshown an automatic connector switch I for completing connection with a group of lines of which that of substation A is a member.'v To the automatic change a line switch C similar to the line switch C of Fig. 1. At La ringer generator is shown, and 4at M is represented a busy signaling machine. v i

In the drawings severalbatteries B are shown, each havingone termi-nalv grounded. There need be only one such battery, however, or preferably one in each exchange.v

The manual substation A may be of any suitable or approved type and, as here shown., comprises the usual receiver 2,switchhook 3, transmitter 4, condenser 5 and ringer 6.' lVhen the receiver is on the hook the c'ir cuit of the transmitter `and receiver-'is open, but when the receiver-is removed the switch hook 3 engages the contact point 7, thereby bridging the ltransmitter and receiver acrossthe line conductors 8 and 9.. v v i The line switch C and master switch D may vbe of the general type disclosed 4in BritishPatent No. 26,301 of 1906, in The American Tclephone'Jou/rnal of New York, N. Y., of June 6, 1908, and in the Western E lectricm of Chicago, Ill'., 'of January 25, 1908, being adapted, however, to operatejin a system in .which no ground connection isV required 'at'the substation. t The line switgh consists essentially of a plunger (not shown) adapted, when released by the energization of the'trip magnet 10, .to enter a .bank of contacts to "force springs 1 1, 13, 15""2 1.n d .17 into contactwith springs' 12,14, -16 and 18, respectively.. -If' the release magnet 19 .be energized after theplungerhas been.v tripped the apparatus willbe placed in condition to withdraw the plunger upon the` following.

' denerg'ization ofthe said magnet 1 9.- In

the 's ystemhere illustratedit is assumed that the lines of a-'numberof's'ubstations leadto a` branch or subeXchange :where each'line is v17 and 18 is shown,.each line `switchisin.

number ofl'suCh- Qsets vof each lset forming "the terminal of 'line' lead-' trunk is multipliedthrough the siimlar bank mon to a group of `substations larger-Kili number than the number: yof trunks: In

order that each lineswitch may always "obtain connection "with -an idle ytrunk,- the' roup of switches that havev access to a particular group oftrunks is. provided witha.

master switch D.

' The masterv sWitch'D vcomprises,-faxnong otherv details, -a ratchet Wheel'20, a motor contacts a, one foreach trunk..v The ratchet.

Wheel 20 is mechanically connected to a magnet 21, circuit controlling relays 22 ,'a1`1d shaft (not shown) in 'such`a manner that a rotarymotion of said wheel .produces a oscillatory motionof the shaft.' The plunger of each line switch is adaptedto.

normally rest in ylocked engagement with.

opposite. the terminal of 'an unoccupied or idle trunk.A Secured to the ratchet wheel 20 "is a notched wheel 11-4 which controls the springs 25 a`nd'26. The' notches in* the `this plunger shaft, andthe masterswitch.

wheel 114 are so spaced'tha-t the springs 25 and 26 will 'be held in contact for all posi.

' tions `of the master switch except when the plungers that are in locked enga-gement With the plunger shaft are in a position directly infront of a trunk terminal.

"The cord circuit O is a ymodified form -of.

theusual' operators cord circuit. The left hand end oflthe cord Ois similar .to many ordinary cords used in Ama'nual'systjems and,

as shown, comprises the plug p, two supervlsoryre'lays 28 a11d29 and the lamp 3 0. The cordis divided into two'parts by the condensers-Sl vand 32..' The right-handend o f the cord comprises a key K, supervisory disclosedin "United- States `LettersPatent operate in' connection 4.with a twowiresys- V tem-etha-tisya system in which no voperatinggro'und isused Aat the substationLxAs here represented', the selector E. compri"se s,`=among ried upon a shaft. (-notfshown) having a ver- .ticalmotion cont-rolledby the vertical magprovided`with aline-switch C.. Althoughonly one set ofsprings 11', 12, 13', 14', 1 5, 16-,.

lector is vcont-'rolled by. the calling voperator through the"! 1ediuin of the doublewouid.

. 98-99, the Wiper 27 maintainsthe corre-f' s-/es aus lines are thus/.extended to the trunk acir- 'euitiis' completed extended from ground Gf.-

(Fig. 2) throughl contactpoint 100, arma'- ture-1'101,--trunk conductor' 98, winding 102 oie relay 95,4 bank. springs 12l and 11, line*- conductor.y 8v4 thence through the substation A.' and back. over`line conductor 9, bank springs 17'an'd 1 8, winding.103v of relay 95,v trunkconductor'99, armature 104,. contact'. peint'105 and'line relay-106,'and thence' through. the battery B 4toground Gl Therelays-'95'and 106 which are vincluded in the circuit just traced'are both energized to attract their respective armatures. The energi'aationof'theline relay 106results. in the closure of afcircuit through thelamp 107, therebys'ignaling-to the operator that her attention 'isdesired onlthis. trunk. The energization' of the relay 95-shifts spring 108 out of .engagement with spring 911 and into 'contact 'with spring 109, whereby the. cir- -1 cuit of the release magnet '-19 is maintained opened,l and the ground Gt isT connected with the vmaster switch bank contact 110 .corresponding to the'trunk seized.- 'As'has 'been previously explained, when the .idle

line switch plungers arejopposite the con-' tacts A of any trunks, in this case trunks spending master switch bank contact 110 in electrical connection 'with the common segment 24.'

an energizing circuit lis completed extend# 'ing ltherefrom through, /Wiper 27 commonsegment 24, motor. magnet :relay 22 to bat-v tery lead'91, thence through the battery B to ground-.(1- The relay 22 energizes upony closure of thiscircuit and forces spring 111 into contact with spring 112, thereby closing an energizing'circ'uit throu'gh-the motor magnet'21 and relay23.' .This circuit extends from ground 'G5 vandl Gre through relay 23. and motor magnet 21'in parallel, 1n-

terrupter springs 113 and relay springs 112k and 4111'to battery lead 91, thence through the battery B teY ground G. The motor magi'ieu'uponv energizing, attracts its armature, which :rotates thev ratchet Wheel one zer. as long as the springs 111 and 112 or 25 and- 26 remain in contact. l

As soon as the ratchet "wheel 20 is rotated its rst step the-spring 26 is forced into contact with spring 25 by a tooth of the notched, wheel 114;.and maintains the energizing circuit ofV the motor magnet 21, irrespective of the springs of relay 22. By the time the spring 2`6fdrops1intothe next notch of the Wheel 1114*. the idle.v lineswitch plungers will have Consequently', when contact point H0 is grounded, asfab'oyeexplaine'd,

reached a. position directly opposite the bank contacts of Athe next'trunk, and the` Wiper 927 will have left the guarded'contact 110,

allowing 'the relay22 rto den'ergize The relay 22 being denergize'd, andthe springs '25 and v 26 separated, the motor magnet ceases to operate and leaves theplungers in.

their positions in front 'of the next trunk after'the one just seized. If this next trunk had been busy, however, the wiper '2 7 would have found a guarding potential upon the Contact succeeding the contact 110, and con` sequently the relay 22 would still have been energized when the springs 25 and 26 were Y separated, the motor magnet would have. continued to operate, the springs 25 and 26 vwouldagain have-been forced-into Contact by the nextltooth.,vr and the plungers would' have' been carried past the busy trunk to an idle one.- The* relay'- 23, Vwhich -is connected in'multiple with the motor magnet.'

'21, energizeswhen its circuit'is rst closed,

butl being a relay that-is slow to denergize.

it remains inl an operated position'as'long .I as the. said magnet is operatin g. l In its vopera-ted position the relay23'v disconnects batteryl from the trip magnets 10 of allthe line switches to whichv the master switch D is allotted. With this arrangement it will be seen that no line switchca'n'be operated while its plunger is being movedto an idle trunk. v

W'hen the, operator at .the main' exchange noticesthe glowing ofthe-lamp 107 she insertsthe plug .2? in the jack j vand throws the keyfK to close thesprings 115 and 116 into contact withv the'springs 117 and 118, respectively, which ,bridges the operator-s talking set S across' the cord O. W'hen the plug pis inserted into the jack j an energizing circuit is closed through the cut-off relay 119. This circuit ofthe' relay 119 ex` tends from ground G7 through relay 119,. 'sleeve springs-of jack y' and-plug p and relay`29- to battery B. The relay 119, upon energizing, attracts its armatures 101 and 101 away from the contacts 100 and 105. and onto contacts and 121, respectively,

whereby the trunk conductors 98 and 99 are disconnected from ground G3' and relay 106,- res'pectively, and are extended -through the jack j tothe cord O. The cutting off of the relay 106 allows said relayto denergize and extinguish thelamp 107.- The relay 29,

' which is included in .the energizing circuit of .the relayv 119, also energizes, vand would close a circuit throughthe lamp 30' but` for i the fact. that therelay 2 8 is energized. at the same time .over a circuit extending from the grounded terminal f of battery 'B' `through relay 28, ti-p springs of plug y) and jackj,"

contact point 120, VarmatureV 101, trunk eon- I ductorV 98, thence throughl substation -A' and Avback over trunk conductor' 9.9., armature 1042 Contact pointA 121, sleevesprings of Jacky and plug p and through relay 29 to the. nongrounded pole of battery B. This latter circuit also-serves to providey the calling substation with talking battery4 current. *i After the operator has ascertained the number of 'the desired line the key K is throivnover to the opposite position and the rplug .21 insertedinto the jack j.d lilith" the key K. in this position the supervisory relay 33 is cut olif' and'the ope'rators set S is bridged across the 'cord' circuit. The insertion of plug p into' jack j completesl an energizing circuit for the line relay -ll of the lirst selector E. This circuit exten ds 'from ground G8 throughA winding ot relay 41, side switch Wiper 4G, trunk conductor 124, ring contacts of i:icl; jl and plug p5, key contacts 125 and, 26, secondary circuit ot theoperators set including the impulse springs 127, thencev through,the'key contacts 12S and 129, tip springs of the plug pand jack j', trunk .confrluctor 130, side switch "Wiper d5 and Winding of the relay ll yto'battery lead '55% the ce through battery B to ground G,

'v-'ilie relay il, upon energizing, shifts the .spring 131 ont of. engagement with the spring 232 f andVVV into Contact with the .rinor 133u ii'herebv froiind is disconnected CJ.

from the release magnet i9 and an energizing circiit is closed'throiigh the release relay 50. This circuit extendsjrom ground G 'through the. springs 131Qand 133 and relay() to battery lead 5l, thence through Y battery B to ground -'G. The relay 50 upon energizing, sl its the'spring 134 out of enf gagenient with the spring 135 and into contact with the spring 136, and closes the spring 137 into contact with the spring 138.

The shitting of the spring 131i shifts the connection oit the impulse spring 132 from the release magnet -l9 to the .vertical magnet 39.' The engagementlot' the springs 137 and 13S extends a connection from groiind'Gl"v 42, springs 13S and 137, trunk conductor 139, sleevecontacts of the jack j and plug if to the relay This ground connection to the relay 3% serves no purpose'at this time except to short-circuit saine. The selector E is 'now in position to receive impulses tor the lirst digit ot the desired-r number.

The operator noiv operates the dial of her i calling device for the digit 2 and, as the impulse Wheel lreturns toiiorinalA position, theimpulse springs 127 are separated twice Each time thefsprings 127 are seplrl they .break the energizing i circuit of relayil of the 'selector Each #11 denergizes the spring .131 ing 133 and momentarilyengages @32. As before explained, the v relay inw to denergize, and consequently ns in its' operated position during l y t intervallthat the springs' 131 and 133 are disengaged.' The engagement Vof i springs 131 and1321closes airenergizingcircuit extending troni l ground i. GP; v`.through springs 131 yandw132, A1li-elan@ ,136;private` vmagnet relay 48, yertical magnet and `side switch wiper-lat to battery lead5l,thence through. battery to ground G. Since the vdigit called'ivas 2 the vertical.4 magnet receives tivo impulses orn the circuit just traced,

vandoperates to raise the switchy shaft and ivipersftivosteps to aposition opposite the secondl bank flevel. Also, as soon'asthe shaft is raised the. lirst step the oil-normal springfl is allowed to engage the Contact point 52, thus connecting the release magnet` t9 with battery. The private magnet relay 8, which ivasrncluded in the energizingcircuit of the vertical magnet, is energizedby 'the iirst impulse, but being a slow-acting rela T',like the-relay 50, does nothave time to denergize betiveen'impulses. lVhen the relay L18. energizes it operates to close an energiziiigcirouit .extending from ground G through .springs 141 and 1&2 and `private magnet i7 to the battery lead 5l, thence through the battery B to ground G. After the last impulse of' the series the line relay breaks the energizing circuit of the private magnet i7, Which'in turn alloivs its .armature to fall back and release theside switch to .Second position. The movement loif side switch Wiper il from first to second position shifts the battery connection. troni the. vertical magnet 89 rto the rotaryfmagnet,40. rlhe rotary magnetis then energized over a circuit extending from ground ils through interrupter springs 1%3, yniagnet i0, vside switch wiper i to battery lead 5l, thence through the battery l); to ground G; and attracts its armature, vvhich rotates the shaft Wipers one step onto the. tirstcontacts of the second level, presses down the private magnet armature and openscthe energizing circuit-of its oivn magnet, lVhenfthe rotary magnet circuit is thus opened theretary armature drops baclihind it ther-lirst trunk leading from the second level ,is idle the armature Vof the private magnet drops baci: also 'and allows the side sivi'tch to pass to 'third position. trunk' ofthe second level is busy lon account of having been seized by some-other selector similar to the select'or;-ll,` thevpri- 'vate Wiper 38 .inds the first contact which it engagesy connectedto ground through ,the

second selector of the busy trunk. 'This `ground is extended by said,.Wiper-overthe If, hoivever, the lirst' l ico i through battery B to ground G. The pricontinue tobe intermittently energized'and denergized to rotate the shaft and wipers step by step until the private )viper 38 reaches a' non-grounded contact of an idle trunk. When an' idle line is, found the private magnet den'erizes and allows the side switch to pass from secondto third position.

'lVhen the side switch wiper 14C leaves its-` second-position contact pointit permanently opens the circuit ofthe rotary magnet 10.

The movement of the side,A switch wipers 4,5 and 46 from secpnd to third position cuts olil the line relay t1 and extends the trunkv conductors and 12% through the shaft Wipers 36 and 37 to the second selector Al?. As soon as the connection is thus extended to the second selector the line lrelay is energized over a circuit extending from ground G11 through Winding 146 of' relay 1415, side switch Wiper v147, shaft wiper 37, side switch Wiper .46 to trunk conductor 124, thence through the operators calling device and hack over trunk conductor 130, side'- switch Wiper Ll5, shaft Wiper .36, side switch wiper 148 and winding 1490i relay 145 to battery lead 51', thence4 throughbattery B to ground G. The relay 145, When energized, operates toshit spring 150 out of engagement with spring 151 and into contact with spring 152, whereby an energizing circuit is closed through the release relay 153. This circuit extends from ground G12 through spring 150 and 152, and Vthrough relay 153 to batter7 lead 54, thence through battery E to ground G. The relay 153, upon energizingv` by closing thecontact between springs 151iand 155, furnishes a new holding ground t'or the. release relay 50 of the first selector E, its former ground being cutoff lby the deenergization of relay 11. The energizing circuit of relay50'now extends from ground G13 atthe selector F, side switch Wiper 156,

relay springs 15,5 and. 154,4', private banlcontact of vthe lseized trunk and -shaftwiper 38, side'sn'ltch Wiper 43 (in third-position), andfthrough relay 50 to battery lead 5ft,

Ithence through lliatteiy. B to vground G. This ground potential furnished by ground G13 to the private bank'contact upon which the Wiper 3S is resting. is extended to the corresponding cont'act in each, of the first selec-A tor banks that are multiplied-withthat ot.'

selector E, for the.purpose of protecting the busyp'trunls from being seized hyany other switch. The foregoing is the position Llanes/8 of the switches immedia-teiylafter the operation of the operate'rs calling device for the iirst digit 2.

lVhen the 'calling device .is operated for the second digit the second selector l? is aim fected in the same mannerv as was the iirst selector for the, irst digit, and operates to 'extend the connection to a repeater H which is included in a trunk line leading to a con .i nector I. Brieiy, the operation of the sec- 75 ond selector is as follows: Each time the line circuit is broken by the impulse springs 127 of the operators calling device, the line re-l lay 145, denerg'izes and closes a circuit from ground. G11 through the private magnet re 30 lay 156and vertical magnet 157 to battery. The second digit being 2 thevertical-inagnet thus receives two impulses and operates to raise the shaft Wipers two steps to a pos' tion opposite the second rou' or level of bank g5 contacts. The relay 153 being slow-acting remains energized during the' entire time the second selector is operating. -Theiprivate magnet relay 1,56 is energized bythe irst impulse to the Vertical magnet,`but,' 9c being a vslow-acting relay, its circuit-*is not opened long enough to permit it to denergize until after the last impulse.. Zhen the relay 156 energizes, by the closure of contact between sprii'igs'158 and 159, it closes an enc5 crgizi'ngeircuit for the private magnet 160. rhis energizing circuit is broken when the relay '156i de'energizes after the last impulse,

the private magnetv 160 denergizes and the side switch passes to second position. The 100 movement of side switch wiper 161 from -iirst to second position shifts the battery connection'from the .Vertical magnet 157 to 'the rotary magnet 162. 1The rotary magnet then ope-rates in the manner explained for ie the rotary magnet 40 of the selector E rto advance the shaft Wipers 163. 164. and- 165 onto the contacts of an idle trunk. fitter thewipers have-reached an idle trunk the side switch is tripped tol third position. and by means of its wipers 117 and 148 extends the line `connection through the shaft Wipers "164 and'163 to the repeater H. At the instant the connection is coi'npletcd tov the'. repeater the relay 55gis energized over a yM5 circuit extending from' ground G21 through -iciuding 1.66, through shaft Wipei'-164,

thence vover the hea Vy conductors through 'selectors F and andthe operatofs calling device, and thence back through switches E and F, and through Windingl? of relay to 'battei'V' lead54, thence' through battery B to ground'Gl` The relay 55, upon energizing, shifts v spring 168 out of engagement with spring 169 and into contact 'with spring 121 170. and forces spring-171 into contact with sp1-ing 172-. The engagement of springs 16S j and 170 closes an energizing circuit from ground G14. through."said 'springs 16S and 170, and through the slow-acting relay 56 to il S Aasiel lfjof flle slowaoting relay v187, privato time Lilie relai; 64 eeriorgizes, agen/cuit is closed "d'ii'oiigliI flie vertan-al Aiiieignet',6%. 'l'his" oirouii, extends froirfi groiid G. through' spriiigsjl and 139, springs '19% iimgse relay ,fertioalmsgnet Gila; side swifcoli wijoor 195 to bit-ery'lead 184, thence through battery B to ground G. Since the digit oslle 2 the versie-il magnet 64 re- Ceies two impulsos over the oirouit just 75 raoed, opor-aies so raise he shaft 'wipers two seps, :incl .allows the off-normal springs 197 close and ooruioc battery to the release k'lflis private magnet relay 195 ,fl liy irs; impulse so the if'erti @nl magnet- 21nd, leiiig slow relay, remains in iis operi-@oai posiiion until all impulses are delivered., Wheiii'r again returns to` iiormal; llhile in -its operated position the relay 195 closes :in energizing circuit from ground G19 "irougii springs lnnfl 199 and, pril-aio magns EGO to o fiery lead 184,- theiioe' 'zfii'oiigli baitery B to ground G. When the prit-'sie magnet denergizes {ift-er the operation of the vertical magno?, it al- 90 lows the sicle sofioli io poss :from rs to seoond position. The passage o'sicle Switch Wiper 196 from irs; so second position shifts the battery Connection from ille Yoriiozil l magnet to tlie rotary iiiagiieii G53, so ilizr; the rotary magnet may be opeiziiecl for the secolnil digit. TNlien the Calling device" is oporaiefl for the lssJ digit the line relay operates in the soms manner as for the tliirl loo `laoli time the relay ill de'riergizes forth@ last cligiiz itioloses o, circuit. from ground- Gls through springs 188 iiiid'lBO'Qll and 193? relay 195 springs 202 ami QOSLrotary mago/es Contact poin. i261 andVl side switch Wiper 196 to battery lead 184, thence' through battery B to grouiid G; 'The' rotary imaginerj u thus receives isn impulses and' operates to rotate ihe shaft Wipers ten sieps y circuit of the .private magnet 200. f The relay 19o doi1 wrgizes in the manner "previ- 'ousiy explained, axial if the called line isidle tlie private magie 200 iiiv turnidenergizes 20 and allows' the siderswiiclito.pass from soeond to iiliirclposition. If, however, tholine iifv is busy when lcalled tho connector sigle switch does not passato:third position, mail the operator is given the busy signal iii the following manner: Whenever o line is lousy, by reason of eitlier having made a call or by liavingbeen called, a guarding ground f poienialis present upon the connector privato bf iks ol that paifticularlie, lnthe i550 the guarded bank Contact to the'ground G18- at thehne relay '6%. f' Ihis shifting of the "holding ground .is for the purpose of pre-` ed 'v 'the line switch C in the same inL je line-switch C (Fig. 1)' furnishes" zie-guar ing potential to the 'private'nornial conductord 93 of 'substation A. The guarding-potential for busy called lines is furnished bythe connector in a man# ""ner to be explained.','Thus, it will be seen that when the connector wipers are `rotated onto the contacts off a'busyline, a ground potential is extended from the guarded. pri-- -vate 'bank'. contact through the shaft wiper.

- 63, side switch vwiper 204, contact 205, relay springs 206` and 207 .and relay 208 to the spring 209 of the private magnet relay'195.

Now, vwhen the private .magnet relay deenergizes, the-spring 199,engages the-spring' 209 .before itbreaks contact with the spring. 198, thus .substituting the ground from the private bank contact forgrtmndxGr19 and'.

maintainingl the private magnet in its energized. posltioxn, which locks the side switch 1n itssecond position, thus preventing the completion of lconnection with the .busy line.v

' The relay 208, which is'included. in. this' last holding. circuit of thefprivate'magnet energizes and, by shifting the spring 207 out v of contact with the Ispring .206 'and into en- ,g'fagement4A with spring 210,' transfers the holding l ground of the private magnet from i' venting two or more'conn'ectors being' advanced to a busy line,`and then all of them 'completingfconnection with they line -if the guardingpotential should be removed beore' the said connectors have vbeen released. vAs' long as the connectorside switch 1s. thus lockedin second'position the 'operator will receiyejthe busy signal. over a circuit extend- -ing fromv batt ry lead5184, through secondary winding of induction coil 211, relay 7 springs 212 'and 218, 'side' switch wiper 214i, ringer relay springs 215 and 216, Acondenser 217,. thence overtheheavy conductors" through'the operators talking set and back, tothe connector, and throughwinding 183' lofl relay .Glto the, starting point.' .Upon hearing -the busy signal, the operator notifies thecalling subscriber and,'by removingi "the plug" p', causesv 'the release of' the switches, as will be explained later.

iBetur-ning now to that stage ofthe .op-

. eration when the connector, wipers had' found the desired line',aIid before' the pri'- vate magnet relay 195 was energized, it willv be explained how 'fthe connection 1s com-- pleted to van idle line. l/Vhenthe private magnet relay'195 denergizes Withthe wipers 'resting on-.an idle line,'it simply opens the energizing circuit of the private magnet 200. `When the private magnet'denergizes.-

v it allows the side switch to pass from second tothird' position,whe1'eby, by-'lm'eans of as soon as the side switch passes to third poi sition. Thus, with-normal operation fof the connector the lamp 185 remainsrlighted onlyine'egsm i Wipers 218 and-214, connection is completed from trunk 'conductorslSO and 181, through condensersi217. and 218a and shaft wipers 61- and62 to the line-conductors 81 and 82. `When theside :switch wiper 204 vpassesvinto third position, it extends a guarding. potential fromground G20 'to wiper 63, 'and thence to theconnector private bank contacts of the called line. The side switch 'wiper 201f(in third position) also closes an energizing cir-` cuit' for the cut-offfrelay 220ii of the line switch C, which relay 'then energizes and gisconnects the 'switch C from the called ne. f v

lllhen theside switch wiper 190 passes from vsecond to third position it@v transfers the battery' connection from the rotary inagnet 65 tothe ringer "relay 67. .'-When the lringer relay is' lthus connected with battery,

said relaybegins tobe intermittently.energized over' acircuit extending'. fr in ground oaf).

G21 through interrupter 221, springs and 223' of relay 05, ringer relay T'and side A switch wipe`r196 to battery-lead 184i, thence 'l through-the battery .B to ground'-G. 'Each time lthe relay' 67 energizes it disconnects the sition the short-circuitis .removed lfrom relay and' said relay is .then energized in' series'with the line relay/6l of the connect'orandl relay 57 of the'repeater H. As previously stated, the relay 06 is of high resistance, yand consequently 'when it enters Y the circuit of relays 0i and` 57 these two relays denergize. v In itsdenergizedposition' the relay' inaintainsfthe short-cirvcuitpf. the resistance175 andv relay '3l of lio thecord circuit 0. .To prevent `the release v of the. connector when the relay 64a deenergiaes, the relay 66 is provided with two whenthe. relay 66 'energizes.

vsprings 224 and 225'which furnish a new-v A .holding ground'for the release relay A-18'7 It is seen that `the relay 68. energizes .and `lights the lamp l 185. as'soon as the connectionis completed tp the connector, but will'ibe denergized y a short tune. If,"however,. the trunk conductors 181 and-1180 should become accidentali-y` crossed, the. lamp will glow-continuously, indicating to theattendant.thatl the trunk isv in trouble. A s soon as the operator completes thereu-` nection thev key. l( is restoredto-norm'alpo" si tion,"y whereby the supervisory .relay l is :through the lmnp 'armature 228. lamp springs o shaft Wiper 62. line conductor Si, spring and SO. primary of induction Coil TQ. trans gniitter 7l, line conductor' SQ, shaft wiper 'l.,

Ito ground (V-l..

y in the' cii'oii'it of the release insegne bridged across the line eratos set. The relajf o3 tliere.ipon enorgizes in series *with the lin j repeater ly :incl operotesto'close E226. 4This tends ironi ground Gg'tlnong'liy con 22e.' come@ nrnitnre 'ESSO to battery l.

Twhen tl'ie subscriber at tlie called substation renio'res his receiver from 'the svfiteli hook'.1 tlint substation is provided with trilliing battery oirrent orer n Circuit extending- 2@ through side Switch Wiper from ground a 20%, Wind l or relay 65, ringer 1 15, side Switch Wiper side sfriteli wiper 218. ringer rela/"springs and '231i' and rfi cling 225;, oi relay G5 to batteri' lead lll. rile to ground (l. 'Tlii lie eon'ipletion' of m'iitof the' rin "er tn'een springs und. the resistance 66. 'llie'iresist-ai 4 and permits en i relayv (5l-to ei i :f it "is soon as the. spring con into Contact with Spring" 189, upon en'ergifmtion of relay 'l the reloj* {3l} becomes -Cirouitecl and clefiixiergizee. ort-ei `t oil reloj; $5 extends from gremial G20? onggli the sairl relnr. springs 5 unal lill. il, mg 88 Sincetlie Winding 179 .of relay (il is nov vconnes-tml to ground direct through springs 23:3 intl L91. 189 mid 15%@ the rela)v 5T of the rep-enter H also receives snllieient current to energize4 lVlien t'ne reupon opens the eira point be Contact, eonneete tli alie relaAv retively low lay 5T energizes it 'separates Springs and tlius removing .the Short-'circuit Vfrom the ref ance 175 :incl the relay ill o the Cord circuit The rel-J5Y 3l and tlie :mee J5 are thus included in ninltipll relays of tli ,selectors The ii'elajf .3-i receives sLicient current over this Circuit to energize nml breaks the Circuit of lmnp armature 3:20a from Contact I The extinguishing of Ianni 226 signifies to the operto' that the Called :subs i aber lios answered. When the calling subseriber hangs up his receiver upon completion or" tlie conversation, the energizing circuit of relays (Fig. l) and 28 (Fig. 2.) is broke-n` Causing the said relays to de'e'nergize. The cleenergization of relay 28 completen the cirreliwY 95 clenergizes, the spring 108 'engages sprinogrl Wliereby an energizing' circuit .1s

closed through the relay 244 and release und.l by closing '"'0'3 by separating tlie'lin upoi initiono said" onorgizzi'tion ol miler' reef; Yer the energiin'g ".C'proirit bridgerel ,f 6' is brokeni'lin'cl'jth Sai again flee ergiies. lllifen* and are''sepeiftiteflr lSWtlieE olf relay the slim-tannini is reinoiecl' the rele-y; G6, ncl saiclie in the. circuit of 'relay (i '57;l theV relzijy G6 again enters "the olie-uit tli"y lay :53' lenergiizes':inclsliorL lay 351- of tlie corel Op X energizee and' again losefs tlf lmnp v226. The simili ai glo 'ing linups intl 226 signiliesftoi tl'ie foperitor t the plugs g), and ifvnmlefrenioil frm-o VVtheir jacks. ll/*lien tliedpln'g isiremoved from. the jack jtli'e circnito'' rele'ys H9 and Q9 is broken anclliotnv elfnyswretuniioo to noijnifil position; When tlie' 'pln'gjjf y removed lfroni tlie the relayl'33 gde-1 energizes anal opens tlielcirouit oflainpvtf, :incl the release oi the'automatie swit'cliesfi's initiated. in tliel following"meunier:1,l lVyli/enrflo the ping j is reino' liroin tliejnekljit Y also breaks the energizing cirenit of tlifline' relay of the i'epeiiterH. "lliefrelzy 55 upon denei'gizing, opensltheenergi"ngvc enit the release. reloj, I" y tween the springs lGS 'andlll encl,'by 'epa rating springsl'i y op SAthle' gizing Circuit of the vreloyp'l o''itlief n neetor l. The relay upon'I derieligii'zingi'Y operates to open the. veirfoi'itol the jre easelll relay 1S. The relayflnpon fcle, riergliing, closes the energizing ,ei'ieni't offreleoee'g magnet 'Tliis circuitn exten'dsf'froin ground Gls through eprin'gs. 1818 1-02 194 and .niagnetfj anclfolnonifzillzo springs 197 to batteryz leeclfl, A5tllenoef through battery Bto groniilf f ,ltf net 186 energizes upon .conifpletr'npoi this cirenitfanfl restores tliefconneY rnieclia'V nisi'n to' normal position, nenit'heswitelilZ shaft reziclies its normalpostiontlie' "springs '1.97. are separated to .elloii the I'ifmqnetI 186A tofclenergi'ize.. VVl'ien tlie'oirenit' .of re'j' lay 56 of ythe repeater isropeneol cle energizesA and opens the circuitfoftl re-k Vil() 'lase relays-153 and 50 thefselectors F and E attal point between the springs 178 and 174. The -relaysi and 50 thereupon denergize and operate vto close theenergizing circuit of the release magnet ot'their re-` spective switches. The circuit of ,the release magnet 2,40 of the selector-F extends from.v

ground G through springs4 131 and 132, 12B/l and 135,. release magnet 4:9 and off-normal springs 52 and 5,1 to battery lead 54, thence through battery B to ground G. The inagnets 240 and 49,upon energizing, cause the release oi' the mechanism of their respective switches, and the said magnets are denergized by the separation of the off-normal springs when the switch shafts reach normal position.

'From the foregoing it will be seen that I vprm'ide a semi-automatic or combined manual and automatic trunking servicelbetween a calling manual subscriber and a called automatic subscriber, and that the said connection is supervised by the manual switchboard operator through the medium of a sigv nal at the manual board, and by meansof circuits controlled by the called subscriber, one of which circuits includes the two Vsides of the trunk line'extending between the second selector and the connector. In this'way the supervisory signal is transferred from the talking circuit to the third conductor or trunk-.release circuit by the repeater H when the called subscriber answers, or when the called subscriber hangs up his receiver. When the called subscriber answers, the resistance 286 at the connector I is switched intocircuit with the conductors of the two- Wire trunk extending from the repeater to the connector, with the result that the relay 57 is denergized. The denergizing of this relay closes a short-circuit around the resistance 175 which" is inseries with the trunkrelease conductors extending back from the repeater to the manual switchboard, where- 'by the relay is energized. This. of course,

serves to retire the supervisory signal 226 at the manual switchboard, advising the operator that the call is answered. lVhen the called subscriber hangs up his-receiver, then the operation is reversed, the resistance Q36 being short-circuited to reduce the resistance of the trunk-release circuit, whereby therelay 57 is energized. This, oi course, brings the resistance 175 into circuit with the trunk-release conductors, causing the denergiz-:ing oi' the relay 34, which results in the clo' ot the local circuit through the ,su-

ie :iso-ry lampsigual '226. The signal thus displayed indicates to the operator that the subscribers are through talking.- Vith this iasaevs arrangement the selectors can'hbe'at one"sta.

"tion and the connecten at another station,

hns Vthe operator has complete supervision-` of a semi-automatic connection involving .only a two-wire trunk between the connectorv and the selectors. The selectors and the manual switchboard can be at the same ex` change, or the said switchboard can-be vat a distant exchange. v

What l claim as my invention is 1. In a telephone system, a talking4 circuit v including a plurality of'trunk lines, means for transmitting a supervisory signal over a port-ion of the talking circuit, a supervisory circuit Aassociated Withone of. said trunk lines. vand means for transferrino the si al.

3. in a telephone system, la-'maiiual switch- Y hoard, a three-conductor trunk line ext-end ing therefrom, a connector, a two-conductor4 trunk line extending to .said connector,

means for connecting the three-conductor i trunk line with the two-conductor trunk line, means 'at the connector responsive to the called subscriber for transmitting asupervisory signal over the two-conductor trunk line, means for transferring the signal from the two-conductor trunlrline tothe third conductor of the o'ther trunk line, which third conductor is excluded from the ico path of voice-currents, and a supervisoryde-` vice located at said switchboard and responl sive to said signal.v i y et. ln a. telephone system, a manual switchboard, a three-conductor trunk line extending Vfrom said switchboard, an automatic connector switch, a two-conductor trunk line trolling the connector over-the said two-'conductor trunk line, means tor transmitting a supervisorysignal over the two-conductor trunk` line. said 4repeater provided with means tor then transferring said signal t0 the third conductor 'of theothei trunk line,

the three-conductor trunk, means at said switchboard, means includin switchboard for receiving said signal, means tor transmitting asupervisory signal over the rst-nientioned two-conductor trunk, asnpervisory device at said switchboard reg a connector Scribner, and another battery for supplying for completing a calling vconnection through the board to the line of a called subscriber, there being a two-conductor trunk line leading to said connector', a supervisory circuit including the two sides ot' said trunk line in series, ieans by which the called subscriber controls said circuit, -a supervisory device located at said switchboard and responsive to said signal, battery with connections'leading through said connector for supplying talknigcurrent to the called subscriber, and another battery for supplying current to the calling subscriber.

l5. ln a telephone system, 'an automatic connector switch, a trunk line ha 'fing only two conductors which lead to said connector switch, means controlled by the called subscriber for transmitting a supervisory signal over said trunk line, suitable means ior receiving said signal, a battery with connections leading through said connector switch for supplying talking current to the called subscriber, and another battery for supplying current to the calling subscriber.

16. In al telephone system, a manual switchboard, la three-conductor trunk line extending therefrom, a connector', a twoconductor trunk line extending to said connector, means tor connectincr the three-conductor trunk line with the two-conductor trunk line, means at thc ccnnector responsive to the called subscriber .for transmitting a supervisory signal over the two-conductor trunk line, means for transferring the signal from the two-conductor trunk line to the third conductor or' the other trunk line, which third conductor is excluded frein the path of voice-currents, a supervisory device located at said .switchboard and responsive to said signal. a battery with connections leading through said connemcr for supplyling talking current to the called subscriber,

and another battery for supplying current to the calling subscriber.

y switchboard, a three-conductor trunk line' 17. lnv a telephone system, a manual A extending from said switchboard, an autothree-conductor trunk line to the two-conf".

ductor trunk line, a repeater for the twolto said signal, a battery with connections conductoritrun'k line, said repeater provided withl means for controlling the connector over the said two-conduct ')rV trunk line, means for transmitting a supervisory signal over the ltlwO-conduictor trunk line, said repeater pravided with meansfor then transferring said 4signal tol the third conductor or. the other trunk line, a supervisory device located at said switchboard and responsive f v leading Athrough said connector switch for supplying talking current to the-called subscriber, and another battery for supplying currentto the calling subscriber.

18. In a telephone system, a manual switchboard, a trunk leading to said board, a calling subscribers line, means for automatically connecting the subscribers line with said trunk, said trunk having only two conductors, a three-conductor vtrunk leading from said switchboard, means by which an operator connects the two-conductor trunk with the three-conductor trunk, a called subscribers line, means including selectors and a connector for finding the called line, there being a two-conductor trunlg leading tothe said connector, meansv for transmitting supervisorysignal over the last-1nenti medy two-conductor trunk, means for then transferring the sinal to thc'third conductor oi' the three-conductor trnirk, means at said switchboard for receiving said signal, means for transmitting a supervisory signal over the Erst-mentioned two-'conductor trunk, a# supervisory device 100 at said switchboard responsive to this signal,

a battery with connections leading through said"-coniiector for supplying talking current to the called subscriber, and another batterywfor supplying current to the calling subscriber.

19. ln a telephone system, means for establishing a connection between a calling and a called subscribers line, said means including a trunk line, an automatic connector switch provided with a resistance, a relay for switching said resistance into circuit with a talking conductor of said trunk line, another relay for controlling a shortcircuit around said resistance, a battery with connections-leading through said connector switch for supplying talking currentto the called subscriber, and another battery for supplying current to the calling subscriber. y

520. In a telephone system, meansv for establishing a connection between aA calling and a called subscribers line, said means-including an automatic connector switch for lindii g the called line, a trunk line having 125 only two conductors leading to said connector switch, means for transmitting a supervisory signal over a talking conductor 0f said trunk line, another trunk line, means for transferring the signal from said first 13o switchboard,

A"ier trunk rete oi tiie voicetn eonneeti iending eil-nin en rent the oelied snbsoiib r.

' ttery for supplying current ioseriieru i tiene sj- Jstein means I'oi'- es teblisliing e sonne tion oetwee -ev calling and e called sniaseri rs line. vsaid ineens 'ni oluding en eutonietio connector switch for linding' seid line, n trunir line lending to vkSani( eonneotor switch, means controlled theV Called subscriber for transmitting i1 'supervisory signal over the two sides oi seid trunk line in series, enotiier trunk "iine provided with more then-two conductors? ineens for trainserring savio swnai from seid iii-si;

trunk line to e Conductor of sind otner trunk line which is not in 'oath' of tiie'iroioe ein-rent@ n; ns i: iid s ii seid toni L s. i current-to ne iied suoseiioer, end en i' in e 'te'elilione system, e, ineens including eonneetor oroompieiing e oelling'oonneotion through the board-to the iine ot e called subscriber, there being two-oondnotor-'trunk line leeding seid Connector, e supervisory oiroiiit including the two sides of said trunk iine in series, ineens by, which the celled sub- `seriloer oontrois said circuit, ey supervisory dei/ice'iffiitefl t sfiid sviJr lib l r bei i @L f -o eine. and ie SPtfflSiv/e to seid sinal, and e.' callin@ ineeneriisni e ceiling ineeneniszn for controlling the two 'sides ot saidtrnni line in series to control said connector switch.

24.111' a telephone system, 'e 'manualswitohboard, e three-conductor trunk line .extending therefrom, a connector, e two! conductor trunk line extending to seid oon- ?iifGQ", .means for oon'ieoting the three-oonduotor'trunk line/with the two-oondnotor trunk line, ineens et the connector responsive to tiie called subscriber for transmitting a supervisory signal over the two-oonduotor trunk iine, ineens for transferring the signel from the two-conduotortrunk line to the third Conductor of the other trunk line which third Conductor is excluded from the 'path of Voiceeurrents a supervisory device located at said switchboard end responsive to said signal. and a calling mechanism for manual I' Y three-conductor trunk line to .heftwoeon- A cluster trunk line, a repezite-i"` eoiniuotor trunk line, 'seid rep vided with ineens for eontrollin i tlz con-- nestor over the seid twooiidne rftrnk line.l ineens 'for transniitting'e isufpervisory signal over the two-f:onduetor ftrinioV s transferring seid signet to the ductorof the other trunk line`,^' deviee located :it seid soons 'f Hed een upervisory ,A-d, v said suliseriiiegs ne, ineens tenentenielieeiy connecting' tlie "l "ibei i. itn seid trunk, seid trunlriiziiingifo conductors, a tliree-oondiiotor trunk e from said. switclibmrd,A Ineens operator Connects the twofoondiito witii the three-conductor triinlrf siilisoribers line, nieensinludin'g and e connector for iindinstliefcelle line, ,there being e two-conductor"trunk l siding" tothe said connector, .ineens trensinitting e supervisory .ngnaloe'iitne len r fentioned two-Conductora*trnn1, ineens for Vthen l,transerriifig the signal tothe tli 'd 'oonduetor oi the three-eondiletor -triinii,fiii'g'ensf et said switchboard `for receiving seid signel,means for transmitting i1 super 'fisory signal over the 5mt-mentioned'two-sondriotor trunk, e supervisory devic e said switchboard responsive to thisvsignl; vfind e calling mechanism vfor, een;trolling two sides oi said trunk yline-'i Control seid'oonnector. .if 27. In al telephone systemfmezins tores tablishing e connection'QloetwVm clling and e called snbsoribers line;V s'zfndjn innin- -oluding e trunk line, an automatic on'nector switch provided with a resistance, a relay for switching said resistance into eircnit with a talking'oonductor of seid trunk line, another relay for controlling e' shortcireuit around said resistance, a Inetallic line circuit, and a Calling mechanism for controlling the two sides of said metallic ,lire circuit in series to control said conneetor switch.

28. lne telephone system,'1neans for esta'blishing'a connection between a calling and. a called subsoribers line, seid means o repeater provided with niensfon'tlienf nd ire:4

tiene;

yincluding an automa'tic connector switch nsupervisory signal' over a talking conductor of said' trunk line, another trunk line, means for transferring the signal from said first trunk line toa conductor of the other trunk line which is not in the path of the voicecurrents, a metallic line circuit, and a calling' mechanism for controlling the two sides of'said metallic line circuit in series to control said connector switch.,

29. lna telephone system, means for establishing a connection between a calling fand a called subscribers line, said means including an automatic connector switch Jfor finding said line, a trunk line leading to said connector` switch, means controlled by the called subscriber for transmitting a supervisory signal over the two sides of said trunk line in series, another trunk line provided with'more than two conductors, means for transferring' said signal from saidl first trunk line to a conductor of said other trunk line whichl is not in the path of the voicecurrents, .means for receiving said signal, a metallicv line circuit, and a calling mechanisni lfor controlling the two sides of said metallic line circuit in series to control said connector switch.

30.` In a telephone system, av manual switchboard, a. three-conductor trunk line extending from said switchboard, an automatic connector switch, a two-conductor trunk line extending to said connector switch, means including first 'and second selectors for extending connection from the three-conductor trunk line to the two-conductor trunk line, a repeaterfor' thetwo. conductor trunk line, said' repeater provided with means for controlling the connector 'over the said two-conductor` trunk line, means for transmitting a supervisory signal said repeater toiicontrol the connector switch.

over the two-conductor 'trunk line, said repeater provided with means for then transferring said signal tothe third-conductor of the other trunk line, a supervisory device lo.- cated at said switchboard and responsive to said signal, land a calling mechanism `for controlling the two sides of'said trunliline -in series to. control said selectors.

manual switchboard, automatic means conn trolledvby the operator for extending conswitchboard, a trunk leading to said bev4 a calling subscribers line, means for matically connecting' the suhscribers line with said trunk, said trunk having only two conductors, a thi'ee-cc'anductory trunk leading ltroni said switchboard, means by which an operator connects the twwconductor trunk with the-three-conductor trunk, a called subscriber-s line, means including selectors and a connector for finding the called line, 'there being a two-conductor trunk leading tothe saidconnector', means foi transmitting a supervisory signal .over the last-mentioned' two-conductor trunk, mea-iis for then translferring the signal to the third conductor oi' the three-conductor trunk, means at said switchboard for receivingsaid signal, mea-ns for transmitting a' supervisory signal over the firstmientioned .two-conductor trunk, a supervisory device at said switchboard .re-v sponsive te this. signal, and a calling mechan isin for controlling the twofsides of saidv trunk line in series to control said selectors.

. In a telephone system, lan automatic connector' switch, aA trunk line having only two conductors leading to said switch, a

nection from said switchboard to said trunk line, means at said board for controlling I said connector over a metallic circuit togli-iid l the line of the called subscriber, and means at saidl switchboard 'for supervising connection. i

33. In a telephone' system, an automatic connector switch, a trunk linehaving 'oily two conductors leading t'o said connector switch, arepeater provided with means for controlling the two sides of said trunk line in series to control said connector, a manual switchboard with the vsaid trunk line,and

switchboard, means for connecting said means at said` switchboard for controlling nii-wann A, Mauritania.'

- l 'l lVitnesses:

EDWARD D. FALns', Aizirrnn J. RAY. 

